The invention relates generally to pulse radars having active electronically scanned array antennas (AESA radars), i.e. pulse radars of the type where the antenna itself is provided with active transmitting elements, and more specifically to a method and an arrangement for increasing the duty cycle of pulse trains from such radars.
Pulse radar transmitters generate pulse trains having a certain peak power and a certain average power. Since such a transmitter operates with a certain peak power, continuous wave (CW) signals cannot normally be generated because the average power of such a signal would be so high that the transmitter would be damaged. In other words, the pulse radar transmitters of today are designed for a maximum duty cycle that cannot be exceeded.
However, there are applications in which it would be advantageous to use a pulse radar also for more or less continuous transmission. It may sometimes be desired to transmit e.g. data via a data link to targets which the radar xe2x80x9cseesxe2x80x9d. To get a reasonably high data transfer rate in such data link applications, it would be necessary to use CW signals or at least pulsed signals having a high duty cycle. Today, it is not possible to use a pulse radar transmitter as the transmitting part in a data link since it cannot transmit the desired CW signal for the reason mentioned above. Instead, in such applications, separate data transmitters have to be used.
There are also other applications, such as jamming of other radar systems, in which it would be advantageous to use pulse radar transmitters for CW operation.
The object of the invention is to enable, in a pulse radar, transmission of pulse trains having a higher duty cycle than what the pulse radar is designed to transmit, and even transmission of a continuous wave signal.
This is generally attained by dividing the aperture of the radar antenna into sub-apertures associated with their own transmitting elements or modules, generating separate pulse trains in the same direction in each sub-aperture, and time shifting the separate pulse trains in such a manner that the pulses of the separate pulse trains form a resulting pulse train having a larger duty cycle than the duty cycle of the separate pulse trains.
Hereby, the use of existing pulse radar systems will be broadened, and the need of special separate data transmitters in connection with pulse radars will be eliminated.